My attic gable fan (http://www.homedepot.com/buy/building-materials/
has a thermostat built in that kicks on when it gets too hot up
there. The fan is powered by a dedicated BX cable that runs up to the
attic, and this cable has a regular wall switch that I can shut on/off
from the 2nd floor hallway. I want the option to run the fan manually
too, bypassing the thermostat. I can replace the BX calbe with a
4wire cable (two hot/one neutral/one ground), and have one of the
wires bypass the thermostat.
But, what kind of wall switch would I need to buy that has, basically,
three settings: off, on (for automatic fan operation via thermostat),
and on (for manual operation of fan, bypassing thermostat)?
Who are you quoting here? It's easier to follow a thread if you quote
and provide the proper attribution.
Tossing out an idea (that the electrical guru's on this board will
either approve or shoot down in flames) - could you use a lighted
If so, it's only the one outlet space and the lighted toggles would
tell you at a glance what was controlling the fan.
You can get a double-wall switch, easily at almost any place that
sells electrical parts, like Home Depot.. Instead of one up-down
switch, it has two side-side switches, one above the other in the same
space as a regular switch. The cover plate is just a duplex outlet
cover plate. I put one in our bathroom, the top switch operates the
ceiling light, the lower switch operates the vanity mirror lights.
You would wire it up so one switched hot lead goes thru the
thermostat, the other switched hot lead goes directly to the motor. if
both switches are off, nothing happens. Simple as falling off a log.
On Wed, 5 Oct 2011 08:30:38 -0700 (PDT), millinghill
You can get two toggle switches that fit in a single box. That's what
I have for my roof fan.
I can turn it off when the stat would turn it on, or on when the stat
would turn it off. I use both features. Normally, when I'm using
neither feature, one of the swtiches is Off and one is On so that the
stat controls things. Eventually I got confused which position was
normal, so I drew a line with an indelible marker across both toggles
in their nomarl position.
You would need three conductors from the swtich to the fan/thermostat.
If you're using BX and there's enough room for one more conductor, you
could solder one of the conductors that is in there to two new ones,
and pull the two through the BX that way. In my house, it's about 8
feet with only a small bit of bending, but be sure to allow a few
feeet extra so you don't pull the wires into the BX. Or have a
helper or better yet tie a big knot in the wires.
If romex is legal where you are, and the BX isn't stapled inside the
wall, you could solder the romex to the BX wires and pull the whole
What the situation calls for is a single pole, double throw switch with
I haven't seen them offered in the form factor of standard 120 volt
toggle switches but I have seen them in the form that mounts in a 1/2"
hole in sheet metal.
BUT "you made me look."
Check out the Levitor 5685-2A. It's a single-pole, double throw,
center off, maintained contact Decora switch.
It might be on the expensive side but with one switch you can choose:
ON, OFF, Thermostat.
You need a on-off-on three posiiton aka center off switch. Not sure
if you can get those with decorator toggles. You might have to get a
regular one at radio shack and mount it in a blank faceplate.
You do not need 4 wires from the box to the fan. You only need three,
two hots and a neutral. You can use regular 14/3.
You wamt to wire the neutral the way it is now. One of the two hots
(black if you use 14/3) will connect the way the existing black hot
wire connects. The second hot (red if you use 14/3) would connect to
the connection between the thermostat and the fan motor, bypassing the
thermostat. On the switch side the original supply hot goes to the
center pole. The two hots (balck and red if you use 14/3) to the fan
go to the other two switch poles.
Now when the switch is inteh center position the fan is off. In one
direction the fan is always on in the other direction the fan is only
on if the thermostat calls for it to be on. Test and then label the
If you just want "auto/on" a regular light switch will work. If you
want a manual off position, you'll need a SPDT switch with a center-
off position. Not sure if those are available in a light switch
format or if you'd need to use a panel mount toggle and mount it in a
hole drilled in a metal blank cover plate.
(firin' up the google machine)
this will work, although not cheap
(Amazon.com product link shortened)
personally if you need the center off I would spend the bucks for a
wall switch... UL listings, code compliance, yadda yadda yadda
An idea: what if I use a single "three-way switch" and have one hot
leg go to the thermostat, and the other hot leg bypass the thermostat?
The only downside is that it will never be "off" unless I kill the
Why would you want to have to turn off the breaker? Isn't there
anything else on that circuit? Using a breaker as a switch is a bad
idea, and running an inexpensive fan constantly is also a bad idea.
What's your issue with a lighted (or not) duplex switch?
Exisitng condition is that I can turn fan off with wall switch.
Reality is that it is only running when it is too hot (thermostat) in
I would only operate this switch to turn the fan OFF if I need to
service the fan or for some emergency.
I would *never* use a breaker on a regular (or even irregular) basis
as a switch.
I think the duplex switch idea is great and will work fine.
I'm only asking about the three-way switch idea because I have a box
of new ones sitting in the garage right now.
On Wed, 5 Oct 2011 11:02:16 -0700 (PDT), millinghill
I keep my roof fan off in the spring and the fall, when it's warm
during the day but would otherwise require heat at night (or
tomorrow), so that the attic heats up and it heats my home. It means
I don't have to use the furnace for a couple weeks times two, four
weeks a year.
EVERYTHING should have an off switch. Back in stone age, we would put
attic fans and lights on switches mounted too high for kids to reach,
right under the scuttle hole. Probably against code now or something.
They were not always ivory levitrons, either, for the fans, Some had a
very industrial toggle or rotator switch- those were probably for the
OTHER kind of attic fan, that sucked hot air out of hallway. Of course,
in some old houses, the hallway and gable fans worked in conjunction.
Thinking back, that might be a lousy idea in a fire- make the entire
house into a chimney. When glowing switches came out, they were very
popular for attic lights, so you could tell off or on without opening
the hatch again.
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